The Beatles' success was largely driven by the songwriting prowess of Paul McCartney and John Lennon. They were the dynamic duo behind the band's phenomenal success, whether they were co-writing or independently crafting songs before sharing them with each other.

A pact made before they rose to fame meant that all songs written by John and Paul were credited to Lennon-McCartney, regardless of whether they were written independently or as a pairing. Despite their success together, the two did not always see eye-to-eye on their songs.